Organic molecules, such as DNA and RNA, can be analyzed utilizing genetic chips that include a matrix of test sites. A single genetic chip may include 1,000 to 500,000 individual test sites. The test sites are individually activated and responses are detected utilizing various activation and detection techniques. One technique for analyzing organic molecules involves combining the molecules with optically active receptors. The optically active receptors are then activated and light emitted from each test site is individually detected and quantified.
One known system for detecting light at a test site includes a charged coupled device (CCD) that is formed in close proximity to each test site. For example, an array of test sites can be formed over a CCD array such that each pixel of the CCD array corresponds to an individual test site. While this optical detection technique works well, there are disadvantages to utilizing CCD arrays.
Although CCD arrays have been widely utilized as image sensors, CCD arrays require specialized processes and equipment for fabrication. CCD arrays are also difficult to integrate with digital and analog circuitry that is designed around standard complementary metal oxide semiconductor (CMOS) technology. In addition, CCD arrays dissipate large amounts of power and may suffer from image smearing problems.
An alternative to a CCD array is active pixel sensor array. Active pixel sensor arrays can be fabricated utilizing CMOS technology and, therefore, can be easily integrated with digital and analog signal processing circuitry. Further, CMOS circuits dissipate smaller amounts of power compared to CCDs.
In view of the disadvantages of CCD arrays and the availability of active pixel sensors, what is needed is a system for optically detecting organic molecules that utilizes active pixel sensors.